Well, according to the update to the post, it's now "One correction. Regarding hikaru’s involvement in Kingdom Hearts III, we are eager to do it. However, our decision is not official yet." Which to be fair is basically a confirmation in all but name. Only a massive catastrophe would deny it at this stage.

And honestly, I'm looking forward to it. Simple and Clean has been remixed so many times I almost forget what the original sounds like.